Pity there's no gas station around when you need one, but Kepler did a lot of great science in it's lifetime. Well done to NASA and Ames, have a frothy one before you look to the future explorations.
Goodnight Kepler! NASA scientists lay the exoplanet expert to rest as it runs out of fuel
The Kepler spacecraft has coughed up its last reserves of fuel and is now retired, after helping scientists discover thousands of exoplanets for nearly a decade, NASA announced on Tuesday. “Fuel exhaustion means it has reached the end of its space life,” Charlie Sobeck, a project system engineer at NASA’s Ames Research Center …
COMMENTS
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Wednesday 31st October 2018 09:20 GMT hammarbtyp
Re: Fuel? Why no solar panels?
Even with solar panels you still need something to push out to move. True, they could of used Ion engines which would of reduced the action mass required, but even that would run out eventually (Smaller mass x higher speed). Also Ion engines are slow and steady, and probably would not be capable of moving a satellite like kepler at the rates required. Fine if you want to reposition over a period of months, but I'm not sure anyone is wanting to wait that long
Finally Kepler has far exceeded its design lifetime, so the engines have done what they needed to do
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Wednesday 31st October 2018 09:24 GMT 0laf
Re: Fuel? Why no solar panels?
I think it's safe to say that the bods at NASA had very good reasons for chosing one form of propulsion over another.
Yet another mission sadly ends although having greatly exeeded its original targets. Some excellent boffinry has been and is being done in our era. Libations for those white coats and engineers who have and are working on such wonderful projects!
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Wednesday 31st October 2018 09:33 GMT Scroticus Canis
Re: Fuel? Why no solar panels?
Oh it has those too. Don't think they were running a mini genset for the electrics :)
With the electrically powered gyros bust they had to use fuel to point the comms at earth just to transfer the collected data, doubled the drain probably.
If they had used imperial gallons it would still have a little life left.
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Thursday 1st November 2018 08:07 GMT Hopalong
Re: Fuel? Why no solar panels?
Solar panels for power, the reaction wheels for fine pointing (powered by the solar panels), then the hydrazine powered RCS for things like unloading the momentum built up in the reaction wheels etc.
The reaction wheels failed over time so it had to use the RCS to do the pointing, which used more hydrazine.
So after 9 1/2 years, it had used up its 11.7 Kg of hydrazine. The camera was failing as well, so it was time for Kepler to retire with a job well done.
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Wednesday 31st October 2018 11:55 GMT Charles 9
Re: Fuel? Why no solar panels?
"But with hindsight, given the beast weighed over a ton, couldn't they have gone for an 8-gallon tank instead?"
When it comes to launching things into space (and believe me, there's just no easy way around beating the Earth's inertia), weight is a very sensitive matter. We're talking ounce-precise calculations and so on due to the cascading problem that it takes fuel to get things into space...but fuel is weight that must be lifted up as well, which takes more fuel, and so on, and so on...
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Wednesday 31st October 2018 17:44 GMT Kevin McMurtrie
Re: Fuel? Why no solar panels?
I'd say the gas mileage was pretty good. Doubling the fuel probably wouldn't help. Some components wear out from radiation or use. Making the components more robust could add so much weight that no amount of fuel can compensate for it (the fuel itself becomes too heavy).
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Wednesday 31st October 2018 14:55 GMT imanidiot
Re: Fuel? Why no solar panels?
It did have reaction wheels to control it's orientation using electrical power. In which case it only needed the fuel to desaturate (spin down) the reaction wheels every once in a while. These are heavy however and the craft only carried one spare (4 total, needing at least 3 for accurate pointing) However, back in 2012 the second of the 4 wheels failed, requiring NASA to find a different way to keep the craft pointing at the target it was observing. They achieved this by carefully "leaning" the craft into the solar wind, then using the remaining reaction wheels to keep it steady in that position. This worked, but because a nearly constant force input from the remaining reaction wheels is required they need to be desaturated much more often, expending more fuel. (Exact details in the NASA paper here: https://keplerscience.arc.nasa.gov/docs/Kepler-2-Wheel-pointing-performance.pdf)
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Wednesday 31st October 2018 18:42 GMT JK63
Re: Fuel? Why no solar panels?
The fuel was for station keeping not for general propulsion. It also has nothing to do with sunshine, which is used to run the platform's electronics packages.
The design life was 3.5 years. They got almost 10 out of the platform. Sorry that nearly 3x the design life isn't acceptable.
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Wednesday 31st October 2018 14:20 GMT 0laf
Re: But why were the transmitters shut down?
They do exactly that. It's part of international agreements with space thingies. When they're done switch 'em off to prevent interference.
Kepler is too far away to be de-orbited but it's also too far away to present much of a problem with regard to Kessler Syndrome. That's a near earth orbit issue.
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Thursday 1st November 2018 10:10 GMT ilmari
Re: But why were the transmitters shut down?
If dead probes weren't shut down, you'd eventually have no frequencies left for new probes to transmit on. So they shut it off, while it's antennas were still pointing close enough towards earth to be able to receive commands.
A US navy navigation satellite launched in 1964 still wakes up occasionally when it gets sunlight on its panels, and transmits telemetry. At its job of navigation satellite it failed 2 months after launch.